The goal of this research program is to elucidate the mechanism(s) by which mitochondrial number, composition and activity change as a function of aging and of diseased state. Mitochondria with altered inner membrane composition will be prepared from chloramphenicol treated, regenerating rat liver. These intact, well coupled, abnormal mitochondria will be biochemically characterized for their lipid composition, energy linked reactions, adenine nucleotide translocase and binding of inhibitors and uncouplers of oxidative phosphorylation. This will help define metabolic consequences of the observed decrease of the inner membrane components. Initial rate studies of succinate oxidation in the presence of ADP do not reveal any differences despite the abnormal mitochondria having only half of its normal complement of cytochrome b, cytochrome oxidase, adenosine triphosphatase and pyridine nucleotide transhydrogenase. In order to detect differences, measurements will be made of substrate oxidations where the mitochondria are kept in a steady state by controlling the external phosphate potential (ATP/ADP x Pi) which will more closely approximate conditions found within the cell. These results will allow better design of experiments to find lesions in 'old' or diseased state mitochondria. The lipid composition and equilibrium binding of uncouplers of oxidative phosphorylation will be used to help explain how these compounds have increased efficiency in the abnormal mitochondria. The synthesis and incoporation of the ATPase into the inner mitochondrial membrane will be studied in detail employing serological and radioisotope labeling techniques as a marker of mitochondrial biosynthesis.